Electrically heated inflatable sleeping mat

ABSTRACT

An inflatable mat includes a compressible inner mat and an airtight shell. One or more heating elements are embedded within the compressible inner mat. Embedding the heating elements within the mat includes removing sections of the inner mat, splitting the sections into upper and lower pieces, inserting the heating elements between the pieces, replacing the section and heating elements to the inner mat, and bonding the airtight shell to the inner mat. Wires embedded in the inner mat conduct electricity from an external power source to the heating elements. The wires may extend primarily around the edges of the inner mat and penetrate into the inner portions of the mat proximate the heating elements. A thermostatic switch and a timer may be interposed between the heating elements and the external power source to control current passing through the heating elements.

FIELD OF THE INVENTION

This invention relates generally to inflatable sleeping mats and, more specifically, to apparatus and methods for heating inflatable sleeping mats.

BACKGROUND OF THE INVENTION

Sleeping mats are critical to the comfort of any backpacker or camper. A sleeping mat provides the user both padding and insulation from the ground. One popular form of sleeping mat includes a foam pad surrounded by an inflatable, wear-resistant outer shell. The foam pad is compressible, enabling air to be driven out of the outer shell and foam to minimize the volume occupied by the mat when packed. Upon inflation, the foam elastically expands the outer shell, drawing in air to facilitate inflation of the mat.

However, during use of such mats, the shoulders and upper back of the user often create pressure points on the mat, compressing the foam pad into a very thin layer. Accordingly, the insulating properties of the mat at such pressure points are very much reduced. Heat from the user's body will therefore tend to escape through these pressure points, resulting in discomfort in these areas. Furthermore, the torso, including the shoulders and upper back, stores much of the thermal energy of the body and supplies thermal energy to the extremities. Accordingly, loss of heat from such areas is likely to result in discomfort at the extremities as well.

Furthermore, the mats are typically made very thin. Backpackers who use such mats typically wish to minimize weight and are willing to sacrifice some of the thickness of the mat to do so. However, reducing the thickness further reduces the insulative properties of the mat.

In view of the foregoing, it would be an advancement in the art to provide an apparatus maintaining the comfort of an user of inflatable foam-core sleeping mats near such pressure points at the upper back and shoulders and at the extremities.

SUMMARY OF THE INVENTION

The present invention comprises a system for heating an inflatable sleeping mat. The mat includes a compressible inner mat and an airtight shell bonded to the inner mat. One or more heating elements embed within the inner mat in the torso or foot regions of the inner mat. One method for embedding heating elements within the mat includes removing a section of the inner mat slightly larger than the heating element. The section is split horizontally into upper and lower pieces. The heating element is placed between the upper and lower pieces and then the upper and lower pieces are returned to the inner mat. The shell is then bonded to the inner mat and retains the section in place.

Wires conduct electricity from an internal or external power source to the heating elements. The wires extend primarily around the edges of the inner mat and penetrate into the inner portions of the mat proximate the heating elements. A horizontal slit may be formed at the edges of the inner mat to receive the wires. Where the wires penetrate the inner portions of the mat, they may pass through holes drilled or otherwise formed in the inner mat.

A thermostatic switch is interposed between the external power source and the heating elements. The thermostatic switch is configured to close when the ambient temperature is below a low threshold and to open when it is above a high threshold. A timer may also be interposed between the external power source and the heating elements. The timer alternately opens and closes in a periodic manner allowing current to pass to the heating elements in short pulses.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.

FIG. 1 is top view of a heated sleeping mat, in accordance with the present invention;

FIG. 2 is a side sectional view of a wire path formed at the edge of the inner mat, in accordance with the present invention;

FIG. 3 is a side sectional view of a wire path through a foam inner mat, in accordance with the present invention;

FIG. 4 is an exploded view of a portion of the heated sleeping mat, in accordance with the present invention;

FIG. 5 is a perspective view of a jack for a plug secured to a heated sleeping mat, in accordance with the present invention;

FIG. 6 is a perspective view of the jack and an integrated thermostat prior to insertion into the heated sleeping mat, in accordance with the present invention;

FIG. 7 is a top view of a heating element, in accordance with the present invention;

FIG. 8 is a top view of a heating element packaged for insertion into a heated sleeping mat, in accordance with the present invention; and

FIG. 9 is a schematic representation of the electrical components of a heated sleeping mat, in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a sleeping mat 10 may include an inner mat 12 and a shell 14. The inner mat 12 is typically formed of a readily compressible foam material. Typically, an open cell foam will be used to permit air to be driven out of the inner mat 12. The inner mat 12 may include a head region 16, torso region 18, and a foot region 20 corresponding approximately to the location of the head, torso, and feet, respectively, of a user reclining on the mat 10. In some embodiments, the inner mat 12 may have meshed regions 22. Meshed regions may be formed at the time the material constituting the mat 12 was formed into sheets, or may be the result of a cutting operation. Meshed regions 22 serve to reduce the weight of the inner mat 12, while still providing an elastic structure for inflating the sleeping mat 10 as discussed below.

The shell 14 typically conforms to the shape of the inner mat 12 and may be bonded to the outer surfaces of the inner mat 12. The shell 14 is typically formed of an airtight material and has an outermost surface that is wear resistant. In some embodiments, the shell 14 is formed of multiple layers, such as an airtight inner layer and a wear resistant outer layer. In the illustrated embodiment, the wear resistant outer layer is formed of nylon, such as a rip-stop nylon commonly used in products made for outdoor use.

A valve 24 secures to the shell 14, typically near the head region 16, and is openable and closable by a user in order to inflate and deflate the sleeping mat 10. In operation, as a user opens the valve 24 the foam forming the inner mat 12 expands, drawing air into the shell 14. A user may further inflate the shell 14 by use of the lungs or a pump. When the proper degree of inflation is reached the user then closes the valve 24. To deflate the sleeping mat 10, the user opens the valve 24 and compresses the inner mat 12 by rolling it tightly, thus forcing the air out of the valve 24. When the sleeping mat 10 is sufficiently deflated, the valve 24 is closed.

In one embodiment of the present invention, one or more heating elements 26 a-26 c are positioned within the shell 14. Heating elements 26 a, 26 b are typically positioned in the torso region 18. Positioning in the torso region 18 may be advantageous due to the role of the torso in regulating body temperature. Warm blood from the torso is carried to extremities and cooler blood from the extremities return to the torso to be heated. Accordingly, locating the heating elements 26 a, 26 b in the torso region 18 permits them to indirectly warm the extremities. Furthermore, pressure points from the back and upper shoulders typically occur within the torso region 18, compressing the inner mat 12 and reducing its insulating properties. Accordingly, positioning the heating elements 26 a, 26 b within the torso region 18 serves to counteract this effect.

In some embodiments, a heating element 26 c may also be positioned in the foot region 20. Inasmuch as the feet are a large distance from the torso, they are susceptible to becoming cold. Accordingly, many users may benefit from positioning the heating element 26 c proximate the feet.

In some embodiments, the inner mat 12 is meshed to reduce its weight. However, in the illustrated embodiment, unmeshed regions 28 a-28 c surround the heating elements 26 a-26 c. The unmeshed regions 28 a-28 c may serve as a sturdy substructure, which the heating elements 26 a-26 c may mount in or on. Unmeshed portions may also be more resistant to compression and therefore provide increased support at pressure points. An additional unmeshed region 30 may be provided in the torso region 18. The unmeshed region 30 may provide material through which cables carrying power to the heating elements 26 a, 26 b may pass. The unmeshed region 30 may also serve to resist compression of the inner mat 12.

Cables 32 a-32 c connect the heating elements 26 a-26 c to an interface 34. The interface 34 pierces the shell 14 and provides a connection point for an exterior power source, such as a battery to connect to the heating elements 26 a- 26 c. The interface 34 may be a socket receiving a plug or a plug for insertion into a socket. In the illustrated embodiment, the interface 34 is flush with, or extends only slightly, from the shell 14. In others, the interface 34 is a wire that extends a substantial distance from the shell 14 and has a plug or socket secured to the end thereof.

In some embodiments, the power source may be an internal battery. Accordingly, the interface 34 may provide an electrical connection for charging the internal battery. In some embodiments, the internal battery is charged by a flexible solar cell secured to the shell 14 or forming part of the shell 14. Accordingly, in such embodiments, an interface 34 may be unnecessary.

Each cable 32 a-32 c typically includes at least a positive and a negative wire. The cables 32 a-32 c extend around the edge of the sleeping mat 10 and extend into the more central portions of the sleeping mat 10 near the heating elements 26 a-26 c. The illustrated arrangement of the cables 32 a-32 c and wires 58 within the inner mat 12 is exemplary. Various other arrangements are possible. For example, the cables 32 a-32 c may extend down the same edge of the inner mat 12 or opposite edges. The wires forming the cables 32 a-32 c may be bound in a common sheath or be separate but follow the same path. Inasmuch as the manufacture of the sleeping mat 10 may expose the cables 32 a-32 c to high temperatures, the sheathing of the wires constituting the cables 32 a-32 c may be made of silicone or other heat resistant materials.

Referring to FIG. 2, the cables 32 a-32 c may extend through slits 36 formed at the edges of the inner mat 12. In some embodiments, the inner mat 12 has meshed regions to reduce the weight of the sleeping mat 10. However, the inner mat 12 may have unmeshed regions proximate the edges. Unmeshed edge regions may facilitate formation of a slit 36 therein to receive the cables 28 a-28 c.

Referring to FIG. 3, the cables 32 a-32 c may extend from near the edges of the inner mat 12 toward the heating elements 26 a-26 c through apertures 38 extending through the inner mat 12. The apertures 38 may be formed by drilling or like means. Alternatively, the apertures 38 may be embodied as slits 38 cut through the inner mat 12. The slits 38 may extend through the inner mat 12 without breaking the upper or lower surface of the inner mat 12 or may be formed by cutting the upper or lower surface of the inner mat 12. The portions of the inner mat 12 in which the apertures 38, or slits 38, are formed may be unmeshed, such as unmeshed regions 28 a, 28 b, and 30.

Referring to FIG. 4, while still referring to FIG. 3, the heating elements 26 a-26 c may be embedded within the inner mat 12. In the illustrated embodiment, a section of the inner mat 12 having a size somewhat larger than one of the heating elements 26 a-26 c is removed from the inner mat 12 for each heating element 26 a-26 c, leaving an aperture 40 in the inner mat 12. The removed sections are divided in the horizontal plane into two pieces 42, 44. The pieces 42, 44 may have different thicknesses 46, 48. The piece 42 may have a thinner thickness 46 to promote conduction of heat therethrough to a user. The piece 44 may have a greater thickness 48 to discourage heat loss to the ground.

In an alternative embodiment, the pieces 42, 44 may be formed of a different material cut to fit within the aperture 40 in the inner mat 12. For example, the piece 42 may be made of a material that is readily compressible or that readily conducts heat, promoting conduction of heat from the heating element 26 a-26 c to the user. The piece 44 may be made of a material that does not conduct heat readily or that is not readily compressible to discourage heat loss to the ground. In some embodiments, additional layers may be positioned between the piece 44 and the shell 14 or between the heating element 26 a-26 c and the piece 44 to discourage heat loss. For example, a layer of reflective material may be used to discourage radiated heat loss to the ground.

The heating element 26 a-26 c may be positioned between the pieces 42, 44, which are then placed within the aperture 40. A cable 32 a-32 c may be passed through an aperture 38 formed in the inner mat 12 to the heating element 26 a-26 c and secured thereto. Alternatively, a cable 32 a-32 c may be first secured to the heating element 26 a-26 c and then passed through the aperture 38, or slit 38.

The shell 14 may then be bonded to the inner mat 12. In some embodiments, bonding the shell 14 to the inner mat 12 requires the application of heat. The application of heat may cause the pieces 42, 44 to bond to the surrounding mat 12 as well as to the shell 14. In other embodiments, the pieces 42, 44 may be adhered to the surrounding inner mat 12 by means of adhesive or heat applied directly to the pieces 42, 44 and inner mat 12. In still other embodiments, the bonding of the shell 14 to the inner mat 12 serves to retain the pieces 42, 44 within the aperture 40.

Referring to FIGS. 5 and 6, the interface 34 may be embodied as a socket 50 having an aperture 52 for receiving a plug electrically coupled to a battery. The socket 50 may be sized to insert into an aperture 54 formed near the head region 16. The aperture 54 may be formed in a rigid block 56 secured to the shell 14. In the illustrated embodiment, the block 56 is formed of molded urethane. The socket 50 has wires 58 extending therefrom, which couple to the cables 32 a-32 c. Alternatively, the cables 32 a-32 c may couple directly to the socket 50. The wires 58 or cables 32 a-32 c may secure to the socket 50 before or after the socket 50 is inserted within the aperture 54. In one method of making the sleeping mat 10, the socket 50 secures to the block 56 and wires 58 or cables 32 a-32 c before the shell 14 is bonded to the inner mat 12. In another method, wires 58 or cables 32 a-32 c are accessible through the aperture 54 and secure to the socket 50 after the shell 14 has been bonded to the inner mat 12.

In some embodiments, a thermostatic switch 60 is secured to the socket 50. For example, the thermostatic switch 60 may be surrounded by molded plastic, which also surrounds portions of the socket 50. Alternatively, the thermostatic switch 60 may be interposed in the conducting path of one of the wires 58 and not secure directly to the socket 50. The thermostatic switch may be designed to close when the ambient temperature is below a certain threshold and to open when the ambient temperature is above a certain threshold. In one embodiment, the low threshold is 20 degrees centigrade and the upper threshold is 25 degrees centigrade.

Referring to FIG. 7, the heating elements 26 a-26 c may be embodied as one or more metallic strips 62 having a positive end 64 and a negative end 66 secured to the positive wire 68 and negative wire 70 of one of the cables 32 a-32 c by means of solder or other fastening means providing electrical conductivity between the ends 64, 66 and the wires 68, 70. The denotation as positive or negative applied to the ends 64, 66 and wires 68, 70 is exemplary; the positive and negative ends 64, 66 may be reversed without altering the function of the heating element 26 a-26 c. The strips 62 may have alternating narrow portions 72 and wide portions 74 along their lengths. The narrow portions 72 have greater resistance and therefore generate heat as current is passed through the strips 62. The wide portions 74 may serve to provide a large area radiating heat away from the heating element 26 a-26 c. In the illustrated embodiment, the two metallic strips 62 constituting the heating elements 26 a, 26 b are designed to consume approximately 2.2 Watts, whereas the heating element 26 c is designed to consume approximately one Watt.

Referring to FIG. 8, the positive end 64 and negative end 66 of the metallic strips 62 may be bound by nonconductive material such as electrical tape 76, or the like, to avoid electrical shock to a user. In some embodiments, the electrical tape 76 secures additional nonconductive material, such as rigid plastic plates over the point of attachment of the cables 32 a-32 c to the metallic strips 62. Additional bands of material, such as electrical tape 72, may surround the metallic strips 62 and wires 68, 70 at a location between the positive end 64 and negative end 66 to maintain the wires 68, 70 and metallic strips 62 in a parallel arrangement. Part or all of the metallic strips 62 may be covered by a sheath 78 formed of plastic or another nonconductive material. The electrical tape 76 may secure the sheath 78 to the metallic strips 62. The wires 68 may also pass through the sheath 78.

Referring to FIG. 9, in the illustrated embodiment, the heating elements 26 a-26 c connect in parallel to a battery 80. In some embodiments, a timer 82 is electrically interposed between the battery 80 and the heating elements 26 a-26 c. The timer 82 may open and close a conduction path between the battery 80 and heating elements 26 a-26 c in periodic intervals of short duration when a voltage is applied thereto. For example, the timer 82 may repeatedly close for two seconds and then open for two seconds. The timer may be disposed near the battery 80, thermostatic switch 60, or at other points in the electrical paths from the battery 80 to the heating elements 26 a-26 c. In the illustrated embodiment, the timer 82 secures to the battery 80 and is embodied as a bimetallic snap switch.

The manner of connecting the heating elements 26 a-26 c, thermostatic switch 60, and timer 82 are exemplary. Many alternative arrangements of the heating elements 26 a-26 c, thermostatic switch 60, timer 82, and connecting cables 32 a-32 c and wires 58 are possible. For example, the heating elements 26 a-26 c, or two of the heating elements 26 a-26 c may connect in series. Separate thermostatic switches 60 may control current flowing to each heating element 26 a-26 c. Likewise, separate timers 82 may also control current flowing to each heating element 26 a-26 c.

While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow. 

1. A sleeping mat comprising: a mat formed of a compressible foam material; and a heat generating element secured to the mat.
 2. The sleeping mat of claim 1, wherein the heat generating element is an electrical heating element.
 3. The sleeping mat of claim 2, wherein the heat generating element is embedded within the mat.
 4. The sleeping mat of claim 3, further comprising a shell formed of an airtight material, the shell enveloping the mat.
 5. The sleeping mat of claim 4, further comprising at least two conduction paths extending from the heat generating element through the shell.
 6. The sleeping mat of claim 5, further comprising a thermostatic switch forming part of at least one of the conduction paths.
 7. The sleeping mat of claim 6, wherein the thermostatic switch is configured to close upon experiencing a low threshold temperature condition and to open upon experiencing a high threshold temperature condition.
 8. The sleeping mat of claim 7, wherein the low threshold temperature condition is an ambient temperature of approximately twenty degrees centigrade and wherein the high threshold temperature condition is an ambient temperature of approximately twenty-five degrees centigrade.
 9. The sleeping mat of claim 8, wherein the conduction paths further comprise a timer configured to open and close for periodic intervals upon application of a voltage thereto.
 10. The sleeping mat of claim 9, wherein the periodic intervals have a duration of approximately two seconds.
 11. A sleeping mat comprising: an inner mat formed of a compressible material, the inner mat having head, torso, and foot portions corresponding to the head, torso, and feet of a person in a prone position; a shell formed of an air tight material enveloping the inner mat and substantially conforming to the shape of the inner mat; a heating element captured within the shell and positioned in the torso portion of the inner mat; and conduction paths extending from the heating element through the shell.
 12. The sleeping mat of claim 11, further comprising a second heating element electrically coupled to the conduction paths and captured within the shell positioned proximate the foot portion of the inner mat.
 13. The sleeping mat of claim 11 further comprising a second heating element electrically coupled to the conduction paths and captured within the shell positioned proximate the torso portion of the inner mat.
 14. The sleeping mat of claim 11, wherein the inner mat is meshed having a region of unmeshed material within the torso portion, the heating element being embedded within the region of unmeshed material.
 15. The sleeping mat of claim 11, further comprising a thermostatic switch forming part of at least one of the conduction paths.
 16. The sleeping mat of claim 15, wherein the thermostatic switch is configured to close upon experiencing a low threshold temperature condition and to open upon experiencing a high threshold temperature condition.
 17. The sleeping mat of claim 16, wherein the low threshold temperature condition is an ambient temperature of approximately twenty degrees centigrade and wherein the high threshold temperature condition is an ambient temperature of approximately twenty-five degrees centigrade.
 18. The sleeping mat of claim 11, wherein at least one of the conduction paths further comprise a timer opening and closing at periodic intervals upon application of a voltage to the at least one conduction path.
 19. The sleeping mat of claim 18, wherein the periodic intervals have a duration of approximately two seconds.
 20. A method for forming a heated sleeping pad, the method comprising: providing an inner mat formed of a sheet of material of substantially uniform thickness; providing a heating element; providing at least two conduction paths; removing a section of the inner mat; providing a heating element; embedding the heating element within the section; coupling the conduction paths to the heating element; replacing the section in the inner mat; and bonding a shell to the exterior surfaces of the inner mat with at least a portion of the conduction paths penetrating the shell.
 21. The method of claim 20, wherein embedding the heating element within the section further comprises: splitting the section into upper and lower pieces in a plane orthogonal to a direction of uniform thickness of the section; and positioning the heating element between the upper and lower pieces.
 22. The method of claim 21, wherein bonding the shell to the inner mat comprises laying the shell over the inner mat and heating the shell and inner mat to a temperature effective to cause fusion of the shell and inner mat. 